Animal Acoustic Communication

Acoustic communication among animals is a major area of focus within the animal bioacoustics community, and, not surprisingly, given the extraordinary diversity of life on a global scale, an abundance of sound production mechanisms and auditory reception and perception strategies have been adopted by the roughly 8.7 million species thought to inhabit the planet, of which 2.2 million are estimated to inhabit the oceans of the world according to a study published recently by Mora and colleagues. Having studied acoustic communication in an exceedingly small fraction of species worldwide, the following decades promise to be a discovery bonanza in this area of inquiry.

The diversity of acoustic communication mechanisms that have evolved among invertebrates alone, a vast group comprising as much as 97% of animal life on the planet, is extraordinary testimony to the remarkable adaptability of animal life; sound generating and reception structures are distributed on most, if not all, body segments and the relative simplicity of the insect nervous system makes for an inviting opportunity to link behavior to neural encoding systems. The great diversity of fish species occupying fresh water and marine environments adds a rich layer of sound to the acoustic backdrop of ponds, rivers, lakes and oceans and, as with insects, fish have evolved a diversity of sound producing, detecting and perceptual systems. Birds, reptiles, amphibians and mammals living in both terrestrial and marine environments have, on the other hand, settled on vocal communication as the preferred acoustic mode of interaction and nuanced differences within those taxa provide fascinating discovery opportunities for the acoustic biologist. While significant inroads have been made in the domain of marine mammal acoustic communication in recent years, understanding the sophisticated and complex nature of systems that have evolved within taxa representing these species remains one of the great challenges of marine bioacousticians, and as in the oceans of the world, the complex acoustic realm created by communicating birds, amphibians and territorial mammals reflects a vibrant, dynamic and biologically diverse planet.

In recent times, the terms geophony, biophony and anthrophony have gained in popularity when considering sound sources that convey critical information relating to intra- and inter-species communication, predation and territoriality. Common natural, geophysical sound sources experienced by faunae are wide-ranging and exhibit highly variable acoustic characteristics. Complementing the rich and varied geophony are the equally rich and varied sounds produced by animals, the biophony. This collection of acoustic signals is as varied as the geophony, with examples ranging from the high pitched evening chorus of insects and dawn songs of many song birds, to the low pitched long distance advertisement calls of mammalian megafauna like the Amur tiger and the humpback whale. The biophony adds a dynamic acoustic layer to the already abundant soundscape of the natural world produced by the physical landscape. Finally, there is the anthrophony, that fraction of the global acoustic budget to which the products of human industry contribute. In the 21st century, animal taxa spanning the entire phylogenetic scale are increasingly facing anthropogenic acoustic challenges. Looking forward, the animal bioacoustics community is positioned to be an essential resource in the effort to balance the interests of biology and modern society.